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Network Working Group                                         P. Congdon
Request for Comments: 3580                       Hewlett Packard Company
Category: Informational                                         B. Aboba
                                                               Microsoft
                                                                <a href='#sA.'>A.</a> Smith
                                                        Trapeze Networks
                                                                 <a href='#sG.'>G.</a> Zorn
                                                           Cisco Systems
                                                                <a href='#sJ.'>J.</a> Roese
                                                               Enterasys
                                                          September 2003


    IEEE 802.1X Remote Authentication Dial In User Service (RADIUS)
                            Usage Guidelines

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

Abstract

   This document provides suggestions on Remote Authentication Dial In
   User Service (RADIUS) usage by IEEE 802.1X Authenticators.  The
   material in this document is also included within a non-normative
   Appendix within the IEEE 802.1X specification, and is being presented
   as an IETF RFC for informational purposes.


















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Table of Contents

   <a href='#s1.'>1.</a>  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  <a href='#p3'>3</a>
       <a href='#s1.1.'>1.1.</a>  Terminology. . . . . . . . . . . . . . . . . . . . . . .  <a href='#p3'>3</a>
       <a href='#s1.2.'>1.2.</a>  Requirements Language. . . . . . . . . . . . . . . . . .  <a href='#p4'>4</a>
   <a href='#s2.'>2.</a>  RADIUS Accounting Attributes . . . . . . . . . . . . . . . . .  <a href='#p5'>5</a>
       <a href='#s2.1.'>2.1.</a>  Acct-Terminate-Cause . . . . . . . . . . . . . . . . . .  <a href='#p5'>5</a>
       <a href='#s2.2.'>2.2.</a>  Acct-Multi-Session-Id. . . . . . . . . . . . . . . . . .  <a href='#p6'>6</a>
       <a href='#s2.3.'>2.3.</a>  Acct-Link-Count. . . . . . . . . . . . . . . . . . . . .  <a href='#p7'>7</a>
   <a href='#s3.'>3.</a>  RADIUS Authentication. . . . . . . . . . . . . . . . . . . . .  <a href='#p7'>7</a>
       <a href='#s3.1.'>3.1.</a>  User-Name. . . . . . . . . . . . . . . . . . . . . . . .  <a href='#p8'>8</a>
       <a href='#s3.2.'>3.2.</a>  User-Password, CHAP-Password, CHAP-Challenge . . . . . .  <a href='#p8'>8</a>
       <a href='#s3.3.'>3.3.</a>  NAS-IP-Address, NAS-IPv6-Address . . . . . . . . . . . .  <a href='#p8'>8</a>
       <a href='#s3.4.'>3.4.</a>  NAS-Port . . . . . . . . . . . . . . . . . . . . . . . .  <a href='#p8'>8</a>
       <a href='#s3.5.'>3.5.</a>  Service-Type . . . . . . . . . . . . . . . . . . . . . .  <a href='#p8'>8</a>
       <a href='#s3.6.'>3.6.</a>  Framed-Protocol. . . . . . . . . . . . . . . . . . . . .  <a href='#p9'>9</a>
       <a href='#s3.7.'>3.7.</a>  Framed-IP-Address, Framed-IP-Netmask . . . . . . . . . .  <a href='#p9'>9</a>
       <a href='#s3.8.'>3.8.</a>  Framed-Routing . . . . . . . . . . . . . . . . . . . . .  <a href='#p9'>9</a>
       <a href='#s3.9.'>3.9.</a>  Filter-ID. . . . . . . . . . . . . . . . . . . . . . . .  <a href='#p9'>9</a>
       <a href='#s3.10.'>3.10.</a> Framed-MTU . . . . . . . . . . . . . . . . . . . . . . .  <a href='#p9'>9</a>
       <a href='#s3.11.'>3.11.</a> Framed-Compression . . . . . . . . . . . . . . . . . . . <a href='#p10'>10</a>
       <a href='#s3.12.'>3.12.</a> Displayable Messages . . . . . . . . . . . . . . . . . . <a href='#p10'>10</a>
       <a href='#s3.13.'>3.13.</a> Callback-Number, Callback-ID . . . . . . . . . . . . . . <a href='#p10'>10</a>
       <a href='#s3.14.'>3.14.</a> Framed-Route, Framed-IPv6-Route. . . . . . . . . . . . . <a href='#p11'>11</a>
       <a href='#s3.15.'>3.15.</a> State, Class, Proxy-State. . . . . . . . . . . . . . . . <a href='#p11'>11</a>
       <a href='#s3.16.'>3.16.</a> Vendor-Specific. . . . . . . . . . . . . . . . . . . . . <a href='#p11'>11</a>
       <a href='#s3.17.'>3.17.</a> Session-Timeout. . . . . . . . . . . . . . . . . . . . . <a href='#p11'>11</a>
       <a href='#s3.18.'>3.18.</a> Idle-Timeout . . . . . . . . . . . . . . . . . . . . . . <a href='#p12'>12</a>
       <a href='#s3.19.'>3.19.</a> Termination-Action . . . . . . . . . . . . . . . . . . . <a href='#p12'>12</a>
       <a href='#s3.20.'>3.20.</a> Called-Station-Id. . . . . . . . . . . . . . . . . . . . <a href='#p12'>12</a>
       <a href='#s3.21.'>3.21.</a> Calling-Station-Id . . . . . . . . . . . . . . . . . . . <a href='#p12'>12</a>
       <a href='#s3.22.'>3.22.</a> NAS-Identifier . . . . . . . . . . . . . . . . . . . . . <a href='#p12'>12</a>
       <a href='#s3.23.'>3.23.</a> NAS-Port-Type. . . . . . . . . . . . . . . . . . . . . . <a href='#p12'>12</a>
       <a href='#s3.24.'>3.24.</a> Port-Limit . . . . . . . . . . . . . . . . . . . . . . . <a href='#p13'>13</a>
       <a href='#s3.25.'>3.25.</a> Password-Retry . . . . . . . . . . . . . . . . . . . . . <a href='#p13'>13</a>
       <a href='#s3.26.'>3.26.</a> Connect-Info . . . . . . . . . . . . . . . . . . . . . . <a href='#p13'>13</a>
       <a href='#s3.27.'>3.27.</a> EAP-Message. . . . . . . . . . . . . . . . . . . . . . . <a href='#p13'>13</a>
       <a href='#s3.28.'>3.28.</a> Message-Authenticator. . . . . . . . . . . . . . . . . . <a href='#p13'>13</a>
       <a href='#s3.29.'>3.29.</a> NAS-Port-Id. . . . . . . . . . . . . . . . . . . . . . . <a href='#p13'>13</a>
       <a href='#s3.30.'>3.30.</a> Framed-Pool, Framed-IPv6-Pool. . . . . . . . . . . . . . <a href='#p14'>14</a>
       <a href='#s3.31.'>3.31.</a> Tunnel Attributes. . . . . . . . . . . . . . . . . . . . <a href='#p14'>14</a>
   <a href='#s4.'>4.</a>  RC4 EAPOL-Key Descriptor . . . . . . . . . . . . . . . . . . . <a href='#p15'>15</a>
   <a href='#s5.'>5.</a>  Security Considerations. . . . . . . . . . . . . . . . . . . . <a href='#p18'>18</a>
       <a href='#s5.1.'>5.1.</a>  Packet Modification or Forgery . . . . . . . . . . . . . <a href='#p18'>18</a>
       <a href='#s5.2.'>5.2.</a>  Dictionary Attacks . . . . . . . . . . . . . . . . . . . <a href='#p19'>19</a>
       <a href='#s5.3.'>5.3.</a>  Known Plaintext Attacks. . . . . . . . . . . . . . . . . <a href='#p19'>19</a>
       <a href='#s5.4.'>5.4.</a>  Replay . . . . . . . . . . . . . . . . . . . . . . . . . <a href='#p20'>20</a>
       <a href='#s5.5.'>5.5.</a>  Outcome Mismatches . . . . . . . . . . . . . . . . . . . <a href='#p20'>20</a>



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       <a href='#s5.6.'>5.6.</a>  802.11 Integration . . . . . . . . . . . . . . . . . . . <a href='#p20'>20</a>
       <a href='#s5.7.'>5.7.</a>  Key Management Issues. . . . . . . . . . . . . . . . . . <a href='#p21'>21</a>
   <a href='#s6.'>6.</a>  IANA Considerations. . . . . . . . . . . . . . . . . . . . . . <a href='#p22'>22</a>
   <a href='#s7.'>7.</a>  References . . . . . . . . . . . . . . . . . . . . . . . . . . <a href='#p22'>22</a>
       <a href='#s7.1.'>7.1.</a>  Normative References . . . . . . . . . . . . . . . . . . <a href='#p22'>22</a>
       <a href='#s7.2.'>7.2.</a>  Informative References . . . . . . . . . . . . . . . . . <a href='#p23'>23</a>
   <a href='#s8.'>8.</a>  Table of Attributes. . . . . . . . . . . . . . . . . . . . . . <a href='#p25'>25</a>
   <a href='#s9.'>9.</a>  Intellectual Property Statement  . . . . . . . . . . . . . . . <a href='#p28'>28</a>
   <a href='#s10.'>10.</a> Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . <a href='#p28'>28</a>
   <a href='#s11.'>11.</a> Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . <a href='#p29'>29</a>
   <a href='#s12.'>12.</a> Full Copyright Statement . . . . . . . . . . . . . . . . . . . <a href='#p30'>30</a>

<h2><a name='s1.'>1.  Introduction</a></h2>

   IEEE 802.1X enables authenticated access to IEEE 802 media, including
   Ethernet, Token Ring, and 802.11 wireless LANs.  Although Remote
   Authentication Dial In User Service (RADIUS) support is optional
   within IEEE 802.1X, it is expected that many IEEE 802.1X
   Authenticators will function as RADIUS clients.

   IEEE 802.1X [IEEE8021X] provides &quot;network port authentication&quot; for
   IEEE 802 [IEEE802] media, including Ethernet [IEEE8023], Token Ring
   and 802.11 [IEEE80211] wireless LANS.

   IEEE 802.1X does not require use of a backend Authentication Server,
   and thus can be deployed with stand-alone bridges or Access Points,
   as well as in centrally managed scenarios.

   In situations where it is desirable to centrally manage
   authentication, authorization and accounting (AAA) for IEEE 802
   networks, deployment of a backend authentication and accounting
   server is desirable.  In such situations, it is expected that IEEE
   <a href='#s802.1X'>802.1X</a> Authenticators will function as AAA clients.

   This document provides suggestions on RADIUS usage by IEEE 802.1X
   Authenticators.  Support for any AAA protocol is optional for IEEE
   <a href='#s802.1X'>802.1X</a> Authenticators, and therefore this specification has been
   incorporated into a non-normative Appendix within the IEEE 802.1X
   specification.

<h2><a name='s1.1.'>1.1.  Terminology</a></h2>

   This document uses the following terms:

   Access Point (AP)
         A Station that provides access to the distribution services via
         the wireless medium for associated Stations.




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   Association
         The service used to establish Access Point/Station mapping and
         enable Station invocation of the distribution system services.

   Authenticator
         An Authenticator is an entity that requires authentication from
         the Supplicant.  The Authenticator may be connected to the
         Supplicant at the other end of a point-to-point LAN segment or
         <a href='#s802.11'>802.11</a> wireless link.

   Authentication Server
         An Authentication Server is an entity that provides an
         Authentication Service to an Authenticator.  This service
         verifies, from the credentials provided by the Supplicant, the
         claim of identity made by the Supplicant.

   Port Access Entity (PAE)
         The protocol entity associated with a physical or virtual
         (802.11) Port.  A given PAE may support the protocol
         functionality associated with the Authenticator, Supplicant or
         both.

   Station (STA)
         Any device that contains an IEEE 802.11 conformant medium
         access control (MAC) and physical layer (PHY) interface to the
         wireless medium (WM).

   Supplicant
         A Supplicant is an entity that is being authenticated by an
         Authenticator.  The Supplicant may be connected to the
         Authenticator at one end of a point-to-point LAN segment or
         <a href='#s802.11'>802.11</a> wireless link.

<h2><a name='s1.2.'>1.2.  Requirements Language</a></h2>

   In this document, several words are used to signify the requirements
   of the specification.  These words are often capitalized.  The key
   words &quot;MUST&quot;, &quot;MUST NOT&quot;, &quot;REQUIRED&quot;, &quot;SHALL&quot;, &quot;SHALL NOT&quot;, &quot;SHOULD&quot;,
   &quot;SHOULD NOT&quot;, &quot;RECOMMENDED&quot;,  &quot;MAY&quot;, and &quot;OPTIONAL&quot; in this document
   are to be interpreted as described in [<A HREF="http://RFC.net/rfc2119.html">RFC2119</A>].











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<h2><a name='s2.'>2.  RADIUS Accounting Attributes</a></h2>

   With a few exceptions, the RADIUS accounting attributes defined in
   [<A HREF="http://RFC.net/rfc2866.html">RFC2866</A>], [<A HREF="http://RFC.net/rfc2867.html">RFC2867</A>], and [<A HREF="http://RFC.net/rfc2869.html">RFC2869</A>] have the same meaning within IEEE
   <a href='#s802.1X'>802.1X</a> sessions as they do in dialup sessions and therefore no
   additional commentary is needed.

   Attributes requiring more discussion include:

      Acct-Terminate-Cause
      Acct-Multi-Session-Id
      Acct-Link-Count

<h2><a name='s2.1.'>2.1.  Acct-Terminate-Cause</a></h2>

   This attribute indicates how the session was terminated, as described
   in [<A HREF="http://RFC.net/rfc2866.html">RFC2866</A>].  [IEEE8021X] defines the following termination cause
   values, which are shown with their RADIUS equivalents in the table on
   the next page.

   IEEE 802.1X                       RADIUS
   dot1xAuthSessionTerminateCause    Acct-Terminate-Cause
   Value                             Value
   -------------                     --------------------
   SupplicantLogoff(1)               User Request (1)
   portFailure(2)                    Lost Carrier (2)
   SupplicantRestart(3)              Supplicant Restart (19)
   reauthFailed(4)                   Reauthentication Failure (20)
   authControlForceUnauth(5)         Admin Reset (6)
   portReInit(6)                     Port Reinitialized (21)
   portAdminDisabled(7)              Port Administratively Disabled (22)
   notTerminatedYet(999)             N/A

   When using this attribute, the User Request (1) termination cause
   corresponds to the situation in which the session terminated due to
   an EAPOL-Logoff received from the Supplicant.  When a session is
   moved due to roaming, the EAPOL state machines will treat this as a
   Supplicant Logoff.

   A Lost Carrier (2) termination cause indicates session termination
   due to loss of physical connectivity for reasons other than roaming
   between Access Points.  For example, if the Supplicant disconnects a
   point-to-point LAN connection, or moves out of range of an Access
   Point, this termination cause is used.  Lost Carrier (2) therefore
   equates to a Port Disabled condition in the EAPOL state machines.

   A Supplicant Restart (19) termination cause indicates
   re-initialization of the Supplicant state machines.



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   A Reauthentication Failure (20) termination cause indicates that a
   previously authenticated Supplicant has failed to re-authenticate
   successfully following expiry of the re-authentication timer or
   explicit re-authentication request by management action.

   Within [IEEE80211], periodic re-authentication may be useful in
   preventing reuse of an initialization vector with a given key.  Since
   successful re-authentication does not result in termination of the
   session, accounting packets are not sent as a result of
   re-authentication unless the status of the session changes.  For
   example:

   a. The session is terminated due to re-authentication failure.  In
      this case the Reauthentication Failure (20) termination cause is
      used.

   b. The authorizations are changed as a result of a successful
      re-authentication.  In this case, the Service Unavailable (15)
      termination cause is used.  For accounting purposes, the portion
      of the session after the authorization change is treated as a
      separate session.

   Where IEEE 802.1X authentication occurs prior to association,
   accounting packets are not sent until an association occurs.

   An Admin Reset (6) termination cause indicates that the Port has been
   administratively forced into the unauthorized state.

   A Port Reinitialized (21) termination cause indicates that the Port's
   MAC has been reinitialized.

   A Port Administratively Disabled (22) termination cause indicates
   that the Port has been administratively disabled.

<h2><a name='s2.2.'>2.2.  Acct-Multi-Session-Id</a></h2>

   The purpose of this attribute is to make it possible to link together
   multiple related sessions.  While [IEEE8021X] does not act on
   aggregated ports, it is possible for a Supplicant roaming between
   Access Points to cause multiple RADIUS accounting packets to be sent
   by different Access Points.

   Where supported by the Access Points, the Acct-Multi-Session-Id
   attribute can be used to link together the multiple related sessions
   of a roaming Supplicant.  In such a situation, if the session context
   is transferred between Access Points, accounting packets MAY be sent
   without a corresponding authentication and authorization exchange,




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   provided that Association has occurred.  However, in such a situation
   it is assumed that the Acct-Multi-Session-Id is transferred between
   the Access Points as part of the Inter-Access Point Protocol (IAPP).

   If the Acct-Multi-Session-Id were not unique between Access Points,
   then it is possible that the chosen Acct-Multi-Session-Id will
   overlap with an existing value allocated on that Access Point, and
   the Accounting Server would therefore be unable to distinguish a
   roaming session from a multi-link session.

   As a result, the Acct-Multi-Session-Id attribute is unique among all
   the bridges or Access Points, Supplicants and sessions.  In order to
   provide this uniqueness, it is suggested that the Acct-Multi-
   Session-Id be of the form:

   Original AP MAC Address | Supplicant MAC Address | NTP Timestamp

   Here &quot;|&quot; represents concatenation, the original AP MAC Address is the
   MAC address of the bridge or Access Point at which the session
   started, and the 64-bit NTP timestamp indicates the beginning of the
   original session.  In order to provide for consistency of the Acct-
   Multi-Session-Id between roaming sessions, the Acct-Multi-Session-Id
   may be moved between Access Points as part of IAPP or another handoff
   scheme.

   The use of an Acct-Multi-Session-Id of this form guarantees
   uniqueness among all Access Points, Supplicants and sessions.  Since
   the NTP timestamp does not wrap on reboot, there is no possibility
   that a rebooted Access Point could choose an Acct-Multi-Session-Id
   that could be confused with that of a previous session.

   Since the Acct-Multi-Session-Id is of type String as defined in
   [<A HREF="http://RFC.net/rfc2866.html">RFC2866</A>], for use with IEEE 802.1X, it is encoded as an ASCII string
   of Hex digits.  Example:  &quot;00-10-A4-23-19-C0-00-12-B2-
   14-23-DE-AF-23-83-C0-76-B8-44-E8&quot;

<h2><a name='s2.3.'>2.3.  Acct-Link-Count</a></h2>

   The Acct-Link-Count attribute may be used to account for the number
   of ports that have been aggregated.

<h2><a name='s3.'>3.  RADIUS Authentication</a></h2>

   This section describes how attributes defined in [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>],
   [<A HREF="http://RFC.net/rfc2867.html">RFC2867</A>], [<A HREF="http://RFC.net/rfc2868.html">RFC2868</A>], [<A HREF="http://RFC.net/rfc2869.html">RFC2869</A>], [<A HREF="http://RFC.net/rfc3162.html">RFC3162</A>] and [<A HREF="http://RFC.net/rfc3579.html">RFC3579</A>] are used in
   IEEE 802.1X authentication.





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<h2><a name='s3.1.'>3.1.  User-Name</a></h2>

   In IEEE 802.1X, the Supplicant typically provides its identity via an
   EAP-Response/Identity message.  Where available, the Supplicant
   identity is included in the User-Name attribute, and included in the
   RADIUS Access-Request and Access-Reply messages as specified in
   [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>] and [<A HREF="http://RFC.net/rfc3579.html">RFC3579</A>].

   Alternatively, as discussed in [<A HREF="http://RFC.net/rfc3579.html">RFC3579</A>] Section 2.1., the User-Name
   attribute may contain the Calling-Station-ID value, which is set to
   the Supplicant MAC address.

<h2><a name='s3.2.'>3.2.  User-Password, CHAP-Password, CHAP-Challenge</a></h2>

   Since IEEE 802.1X does not support PAP or CHAP authentication, the
   User-Password, CHAP-Password or CHAP-Challenge attributes are not
   used by IEEE 802.1X Authenticators acting as RADIUS clients.

<h2><a name='s3.3.'>3.3.  NAS-IP-Address, NAS-IPv6-Address</a></h2>

   For use with IEEE 802.1X, the NAS-IP-Address contains the IPv4
   address of the bridge or Access Point acting as an Authenticator, and
   the NAS-IPv6-Address contains the IPv6 address.  If the IEEE 802.1X
   Authenticator has more than one interface, it may be desirable to use
   a loopback address for this purpose so that the Authenticator will
   still be reachable even if one of the interfaces were to fail.

<h2><a name='s3.4.'>3.4.  NAS-Port</a></h2>

   For use with IEEE 802.1X the NAS-Port will contain the port number of
   the bridge, if this is available.  While an Access Point does not
   have physical ports, a unique &quot;association ID&quot; is assigned to every
   mobile Station upon a successful association exchange.  As a result,
   for an Access Point, if the association exchange has been completed
   prior to authentication, the NAS-Port attribute will contain the
   association ID, which is a 16-bit unsigned integer.  Where IEEE
   <a href='#s802.1X'>802.1X</a> authentication occurs prior to association, a unique NAS-Port
   value may not be available.

<h2><a name='s3.5.'>3.5.  Service-Type</a></h2>

   For use with IEEE 802.1X, the Framed (2), Authenticate Only (8), and
   Call Check (10) values are most commonly used.

   A Service-Type of Framed indicates that appropriate 802 framing
   should be used for the connection.  A Service-Type of Authenticate
   Only (8) indicates that no authorization information needs to be
   returned in the Access-Accept.  As described in [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>], a



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   Service-Type of Call Check is included in an Access-Request packet to
   request that the RADIUS server accept or reject the connection
   attempt, typically based on the Called-Station-ID (set to the bridge
   or Access Point MAC address) or Calling-Station-ID attributes (set to
   the Supplicant MAC address).  As noted in [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>], it is
   recommended that in this case, the User-Name attribute be given the
   value of Calling-Station-Id.

<h2><a name='s3.6.'>3.6.  Framed-Protocol</a></h2>

   Since there is no value for IEEE 802 media, the Framed-Protocol
   attribute is not used by IEEE 802.1X Authenticators.

<h2><a name='s3.7.'>3.7.  Framed-IP-Address, Framed-IP-Netmask</a></h2>

   IEEE 802.1X does not provide a mechanism for IP address assignment.
   Therefore the Framed-IP-Address and Framed-IP-Netmask attributes can
   only be used by IEEE 802.1X Authenticators that support IP address
   assignment mechanisms.  Typically this capability is supported by
   layer 3 devices.

<h2><a name='s3.8.'>3.8.  Framed-Routing</a></h2>

   The Framed-Routing attribute indicates the routing method for the
   Supplicant.  It is therefore only relevant for IEEE 802.1X
   Authenticators that act as layer 3 devices, and cannot be used by a
   bridge or Access Point.

<h2><a name='s3.9.'>3.9.  Filter-ID</a></h2>

   This attribute indicates the name of the filter list to be applied to
   the Supplicant's session.  For use with an IEEE 802.1X Authenticator,
   it may be used to indicate either layer 2 or layer 3 filters.  Layer
   3 filters are typically only supported on IEEE 802.1X Authenticators
   that act as layer 3 devices.

<h2><a name='s3.10.'>3.10.  Framed-MTU</a></h2>

   This attribute indicates the maximum size of an IP packet that may be
   transmitted over the wire between the Supplicant and the
   Authenticator.  IEEE 802.1X Authenticators set this to the value
   corresponding to the relevant 802 medium, and include it in the
   RADIUS Access-Request.  The RADIUS server may send an EAP packet as
   large as Framed-MTU minus four (4) octets, taking into account the
   additional overhead for the IEEE 802.1X Version (1), Type (1) and
   Body Length (2) fields.  For EAP over IEEE 802 media, the Framed-MTU
   values (which do not include LLC/SNAP overhead) and maximum frame
   length values (not including the preamble) are as follows:



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                                        Maximum Frame
   Media             Framed-MTU            Length
   =========        ===============     ==============
   Ethernet              1500              1522
   <a href='#s802.3'>802.3</a>                 1500              1522
   <a href='#s802.4'>802.4</a>                 8174              8193
   <a href='#s802.5'>802.5</a> (4 Mbps)        4528              4550
   <a href='#s802.5'>802.5</a> (16 Mbps)      18173             18200
   <a href='#s802.5'>802.5</a> (100 Mb/s)     18173             18200
   <a href='#s802.6'>802.6</a>                 9191              9240
   802.9a                1500              1518
   <a href='#s802.11'>802.11</a>                2304              2346
   <a href='#s802.12'>802.12</a> (Ethernet)     1500              1518
   <a href='#s802.12'>802.12</a> (Token Ring)   4502              4528
   FDDI                  4479              4500

   NOTE - the Framed-MTU size for IEEE 802.11 media may change as a
   result of ongoing work being undertaken in the IEEE 802.11 Working
   Group.  Since some 802.11 stations cannot handle an MTU larger than
   1500 octets, it is recommended that RADIUS servers encountering a
   NAS-Port-Type value of 802.11 send EAP packets no larger than 1496
   octets.

<h2><a name='s3.11.'>3.11.  Framed-Compression</a></h2>

   [IEEE8021X] does not include compression support.  Therefore this
   attribute is not understood by [IEEE8021X] Authenticators.

<h2><a name='s3.12.'>3.12.  Displayable Messages</a></h2>

   The Reply-Message attribute, defined in section 5.18 of [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>],
   indicates text which may be displayed to the user.  This is similar
   in concept to the EAP Notification Type, defined in [<A HREF="http://RFC.net/rfc2284.html">RFC2284</A>].  As
   noted in [<A HREF="http://RFC.net/rfc3579.html">RFC3579</A>], Section 2.6.5, when sending a displayable message
   to an [IEEE8021X] Authenticator, displayable messages are best sent
   within EAP-Message/EAP-Request/Notification attribute(s), and not
   within Reply-Message attribute(s).

<h2><a name='s3.13.'>3.13.  Callback-Number, Callback-ID</a></h2>

   These attributes are not understood by IEEE 802.1X Authenticators.










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<h2><a name='s3.14.'>3.14.  Framed-Route, Framed-IPv6-Route</a></h2>

   The Framed-Route and Framed-IPv6-Route attributes provide routes that
   are to be configured for the Supplicant.  These attributes are
   therefore only relevant for IEEE 802.1X Authenticators that act as
   layer 3 devices, and cannot be understood by a bridge or Access
   Point.

<h2><a name='s3.15.'>3.15.  State, Class, Proxy-State</a></h2>

   These attributes are used for the same purposes as described in
   [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>].

<h2><a name='s3.16.'>3.16.  Vendor-Specific</a></h2>

   Vendor-specific attributes are used for the same purposes as
   described in [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>].  The MS-MPPE-Send-Key and MS-MPPE-Recv-Key
   attributes, described in section 2.4 of [<A HREF="http://RFC.net/rfc2548.html">RFC2548</A>], MAY be used to
   encrypt and authenticate the RC4 EAPOL-Key descriptor [IEEE8021X,
   Section 7.6].  Examples of the derivation of the MS-MPPE-Send-Key and
   MS-MPPE-Recv-Key attributes from the master key negotiated by an EAP
   method are given in [<A HREF="http://RFC.net/rfc2716.html">RFC2716</A>].  Details of the EAPOL-Key descriptor
   are provided in Section 4.

<h2><a name='s3.17.'>3.17.  Session-Timeout</a></h2>

   When sent along in an Access-Accept without a Termination-Action
   attribute or with a Termination-Action attribute set to Default, the
   Session-Timeout attribute specifies the maximum number of seconds of
   service provided prior to session termination.

   When sent in an Access-Accept along with a Termination-Action value
   of RADIUS-Request, the Session-Timeout attribute specifies the
   maximum number of seconds of service provided prior to re-
   authentication.  In this case, the Session-Timeout attribute is used
   to load the reAuthPeriod constant within the Reauthentication Timer
   state machine of 802.1X.  When sent with a Termination-Action value
   of RADIUS-Request, a Session-Timeout value of zero indicates the
   desire to perform another authentication (possibly of a different
   type) immediately after the first authentication has successfully
   completed.

   When sent in an Access-Challenge, this attribute represents the
   maximum number of seconds that an IEEE 802.1X Authenticator should
   wait for an EAP-Response before retransmitting.  In this case, the
   Session-Timeout attribute is used to load the suppTimeout constant
   within the backend state machine of IEEE 802.1X.




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<h2><a name='s3.18.'>3.18.  Idle-Timeout</a></h2>

   The Idle-Timeout attribute is described in [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>].  For IEEE 802
   media other than 802.11 the media are always on.  As a result the
   Idle-Timeout attribute is typically only used with wireless media
   such as IEEE 802.11.  It is possible for a wireless device to wander
   out of range of all Access Points.  In this case, the Idle-Timeout
   attribute indicates the maximum time that a wireless device may
   remain idle.

<h2><a name='s3.19.'>3.19.  Termination-Action</a></h2>

   This attribute indicates what action should be taken when the service
   is completed.  The value RADIUS-Request (1) indicates that re-
   authentication should occur on expiration of the Session-Time.  The
   value Default (0) indicates that the session should terminate.

<h2><a name='s3.20.'>3.20.  Called-Station-Id</a></h2>

   For IEEE 802.1X Authenticators, this attribute is used to store the
   bridge or Access Point MAC address in ASCII format (upper case only),
   with octet values separated by a &quot;-&quot;.  Example: &quot;00-10-A4-23-19-C0&quot;.
   In IEEE 802.11, where the SSID is known, it SHOULD be appended to the
   Access Point MAC address, separated from the MAC address with a &quot;:&quot;.
   Example &quot;00-10-A4-23-19-C0:AP1&quot;.

<h2><a name='s3.21.'>3.21.  Calling-Station-Id</a></h2>

   For IEEE 802.1X Authenticators, this attribute is used to store the
   Supplicant MAC address in ASCII format (upper case only), with octet
   values separated by a &quot;-&quot;.  Example: &quot;00-10-A4-23-19-C0&quot;.

<h2><a name='s3.22.'>3.22.  NAS-Identifier</a></h2>

   This attribute contains a string identifying the IEEE 802.1X
   Authenticator originating the Access-Request.

<h2><a name='s3.23.'>3.23.  NAS-Port-Type</a></h2>

   For use with IEEE 802.1X, NAS-Port-Type values of Ethernet (15)
   Wireless - IEEE 802.11 (19), Token Ring (20) and FDDI (21) may be
   used.









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<h2><a name='s3.24.'>3.24.  Port-Limit</a></h2>

   This attribute has no meaning when sent to an [IEEE8021X]
   Authenticator.

<h2><a name='s3.25.'>3.25.  Password-Retry</a></h2>

   In IEEE 802.1X, the Authenticator always transitions to the HELD
   state after an authentication failure.  Thus this attribute does not
   make sense for IEEE 802.1X.

<h2><a name='s3.26.'>3.26.  Connect-Info</a></h2>

   This attribute is sent by a bridge or Access Point to indicate the
   nature of the Supplicant's connection.  When sent in the Access-
   Request it is recommended that this attribute contain information on
   the speed of the Supplicant's connection.  For 802.11, the following
   format is recommended: &quot;CONNECT 11Mbps 802.11b&quot;.  If sent in the
   Accounting STOP, this attribute may be used to summarize statistics
   relating to session quality.  For example, in IEEE 802.11, the
   Connect-Info attribute may contain information on the number of link
   layer retransmissions.  The exact format of this attribute is
   implementation specific.

<h2><a name='s3.27.'>3.27.  EAP-Message</a></h2>

   Since IEEE 802.1X provides for encapsulation of EAP as described in
   [<A HREF="http://RFC.net/rfc2284.html">RFC2284</A>] and [IEEE8021X], the EAP-Message attribute defined in
   [<A HREF="http://RFC.net/rfc3579.html">RFC3579</A>] is used to encapsulate EAP packets for transmission from
   the IEEE 802.1X Authenticator to the Authentication Server. [<A HREF="http://RFC.net/rfc3579.html">RFC3579</A>]
   Section 2.2. describes how the Authentication Server handles invalid
   EAP packets passed to it by the Authenticator.

<h2><a name='s3.28.'>3.28.  Message-Authenticator</a></h2>

   As noted in [<A HREF="http://RFC.net/rfc3579.html">RFC3579</A>] Section 3.1., the Message-Authenticator
   attribute MUST be used to protect packets within a RADIUS/EAP
   conversation.

<h2><a name='s3.29.'>3.29.  NAS-Port-Id</a></h2>

   This attribute is used to identify the IEEE 802.1X Authenticator port
   which authenticates the Supplicant.  The NAS-Port-Id differs from the
   NAS-Port in that it is a string of variable length whereas the NAS-
   Port is a 4 octet value.






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<h2><a name='s3.30.'>3.30.  Framed-Pool, Framed-IPv6-Pool</a></h2>

   IEEE 802.1X does not provide a mechanism for IP address assignment.
   Therefore the Framed-Pool and Framed-IPv6-Pool attributes can only be
   used by IEEE 802.1X Authenticators that support IP address assignment
   mechanisms.  Typically this capability is supported by layer 3
   devices.

<h2><a name='s3.31.'>3.31.  Tunnel Attributes</a></h2>

   Reference [<A HREF="http://RFC.net/rfc2868.html">RFC2868</A>] defines RADIUS tunnel attributes used for
   authentication and authorization, and [<A HREF="http://RFC.net/rfc2867.html">RFC2867</A>] defines tunnel
   attributes used for accounting.  Where the IEEE 802.1X Authenticator
   supports tunneling, a compulsory tunnel may be set up for the
   Supplicant as a result of the authentication.

   In particular, it may be desirable to allow a port to be placed into
   a particular Virtual LAN (VLAN), defined in [IEEE8021Q], based on the
   result of the authentication.  This can be used, for example, to
   allow a wireless host to remain on the same VLAN as it moves within a
   campus network.

   The RADIUS server typically indicates the desired VLAN by including
   tunnel attributes within the Access-Accept.  However, the IEEE 802.1X
   Authenticator may also provide a hint as to the VLAN to be assigned
   to the Supplicant by including Tunnel attributes within the Access-
   Request.

   For use in VLAN assignment, the following tunnel attributes are used:

   Tunnel-Type=VLAN (13)
   Tunnel-Medium-Type=802
   Tunnel-Private-Group-ID=VLANID

   Note that the VLANID is 12-bits, taking a value between 1 and 4094,
   inclusive.  Since the Tunnel-Private-Group-ID is of type String as
   defined in [<A HREF="http://RFC.net/rfc2868.html">RFC2868</A>], for use with IEEE 802.1X, the VLANID integer
   value is encoded as a string.

   When Tunnel attributes are sent, it is necessary to fill in the Tag
   field.  As noted in [<A HREF="http://RFC.net/rfc2868.html">RFC2868</A>], section 3.1:

      The Tag field is one octet in length and is intended to provide a
      means of grouping attributes in the same packet which refer to the
      same tunnel.  Valid values for this field are 0x01 through 0x1F,
      inclusive.  If the Tag field is unused, it MUST be zero (0x00).





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   For use with Tunnel-Client-Endpoint, Tunnel-Server-Endpoint, Tunnel-
   Private-Group-ID, Tunnel-Assignment-ID, Tunnel-Client-Auth-ID or
   Tunnel-Server-Auth-ID attributes (but not Tunnel-Type, Tunnel-
   Medium-Type, Tunnel-Password, or Tunnel-Preference), a tag field of
   greater than 0x1F is interpreted as the first octet of the following
   field.

   Unless alternative tunnel types are provided, (e.g. for IEEE 802.1X
   Authenticators that may support tunneling but not VLANs), it is only
   necessary for tunnel attributes to specify a single tunnel.  As a
   result, where it is only desired to specify the VLANID, the tag field
   SHOULD be set to zero (0x00) in all tunnel attributes.  Where
   alternative tunnel types are to be provided, tag values between 0x01
   and 0x1F SHOULD be chosen.

<h2><a name='s4.'>4.  RC4 EAPOL-Key Frame</a></h2>

   The RC4 EAPOL-Key frame is created and transmitted by the
   Authenticator in order to provide media specific key information.
   For example, within 802.11 the RC4 EAPOL-Key frame can be used to
   distribute multicast/broadcast (&quot;default&quot;) keys, or unicast (&quot;key
   mapping&quot;) keys.  The &quot;default&quot; key is the same for all Stations
   within a broadcast domain.

   The RC4 EAPOL-Key frame is not acknowledged and therefore the
   Authenticator does not know whether the Supplicant has received it.
   If it is lost, then the Supplicant and Authenticator will not have
   the same keying material, and communication will fail.  If this
   occurs, the problem is typically addressed by re-running the
   authentication.

   The RC4 EAPOL-Key frame is sent from the Authenticator to the
   Supplicant in order to provision the &quot;default&quot; key, and subsequently
   in order to refresh the &quot;default&quot; key.  It may also be used to
   refresh the key-mapping key.  Rekey is typically only required with
   weak ciphersuites such as WEP, defined in [IEEE80211].

   Where keys are required, an EAP method that derives keys is typically
   selected.  Therefore the initial &quot;key mapping&quot; keys can be derived
   from EAP keying material, without requiring the Authenticator to send
   an RC4 EAPOL-Key frame to the Supplicant.  An example of how EAP
   keying material can be derived and used is presented in [<A HREF="http://RFC.net/rfc2716.html">RFC2716</A>].









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   While the RC4 EAPOL-Key frame is defined in [IEEE8021X], a more
   complete description is provided on the next page.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Version    |  Packet Type  |  Packet Body Length           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |          Key  Length          |Replay Counter...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Replay Counter...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Replay Counter    |   Key IV...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Key IV...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Key IV...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Key IV...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Key IV...         |F| Key Index   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Key Signature...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Key Signature...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Key Signature...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Key Signature...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Key...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Version
      The Version field is one octet.  For IEEE 802.1X, it contains the
      value 0x01.

   Packet Type
      The Packet Type field is one octet, and determines the type of
      packet being transmitted.  For an EAPOL-Key Descriptor, the Packet
      Type field contains 0x03.

   Packet Body Length
      The Packet Body Length is two octets, and contains the length of
      the EAPOL-Key descriptor in octets, not including the Version,
      Packet Type and Packet Body Length fields.





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   Type
      The Type field is a single octet.  The Key descriptor is defined
      differently for each Type; this specification documents only the
      RC4 Key Descriptor (Type = 0x01).

   Key Length
      The Key Length field is two octets.  If Packet Body Length = 44 +
      Key Length, then the Key Field contains the key in encrypted form,
      of length Key Length.  This is 5 octets (40 bits) for WEP, and 13
      octets (104 bits) for WEP-128.  If Packet Body Length = 44, then
      the Key field is absent, and Key Length represents the number of
      least significant octets from the MS-MPPE-Send-Key attribute
      [<A HREF="http://RFC.net/rfc2548.html">RFC2548</A>] to be used as the keying material.  Note that the MS-
      MPPE-Send-Key and MS-MPPE-Recv-Key attributes are defined from the
      point of view of the Authenticator.  From the Supplicant point of
      reference, the terms are reversed.  Thus the MS-MPPE-Recv-Key on
      the Supplicant corresponds to the MS-MPPE-Send-Key on the
      Authenticator, and the MS-MPPE-Send-Key on the Supplicant
      corresponds to the MS-MPPE-Recv-Key on the Authenticator.

   Replay Counter
      The Replay Counter field is 8 octets.  It does not repeat within
      the life of the keying material used to encrypt the Key field and
      compute the Key Signature field.  A 64-bit NTP timestamp MAY be
      used as the Replay Counter.

   Key IV
      The Key IV field is 16 octets and includes a 128-bit
      cryptographically random number.

   F
      The Key flag (F) is a single bit, describing the type of key that
      is included in the Key field.  Values are:

      0 = for broadcast (default key)
      1 = for unicast (key mapping key)

   Key Index
      The Key Index is 7 bits.

   Key Signature
      The Key Signature field is 16 octets.  It contains an HMAC-MD5
      message integrity check computed over the EAPOL-Key descriptor,
      starting from the Version field, with the Key field filled in if
      present, but with the Key Signature field set to zero.  For the
      computation, the 32 octet (256 bit) MS-MPPE-Send-Key [<A HREF="http://RFC.net/rfc2548.html">RFC2548</A>] is
      used as the HMAC-MD5 key.




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   Key
      If Packet Body Length = 44 + Key Length, then the Key Field
      contains the key in encrypted form, of length Key Length.  If
      Packet Body Length = 44, then the Key field is absent, and the
      least significant Key Length octets from the MS-MPPE-Send-Key
      attribute is used as the keying material.  Where the Key field is
      encrypted using RC4, the RC4 encryption key used to encrypt this
      field is formed by concatenating the 16 octet (128 bit) Key-IV
      field with the 32 octet MS-MPPE-Recv-Key attribute.  This yields a
      48 octet RC4 key (384 bits).

<h2><a name='s5.'>5.  Security Considerations</a></h2>

   Since this document describes the use of RADIUS for purposes of
   authentication, authorization, and accounting in IEEE 802.1X-enabled
   networks, it is vulnerable to all of the threats that are present in
   other RADIUS applications.  For a discussion of these threats, see
   [<A HREF="http://RFC.net/rfc2607.html">RFC2607</A>], [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>], [<A HREF="http://RFC.net/rfc3162.html">RFC3162</A>], [<A HREF="http://RFC.net/rfc3579.html">RFC3579</A>], and [<A HREF="http://RFC.net/rfc3576.html">RFC3576</A>].

   Vulnerabilities include:

      Packet modification or forgery
      Dictionary attacks
      Known plaintext attacks
      Replay
      Outcome mismatches
      <a href='#s802.11'>802.11</a> integration
      Key management issues

<h2><a name='s5.1.'>5.1.  Packet Modification or Forgery</a></h2>

   RADIUS, defined in [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>], does not require all Access-Requests to
   be authenticated or integrity protected.  However, IEEE 802.1X is
   based on EAP.  As described in [3579], Section 3.1.:

      The Message-Authenticator attribute MUST be used to protect all
      Access-Request, Access-Challenge, Access-Accept, and Access-Reject
      packets containing an EAP-Message attribute.

   As a result, when used with IEEE 802.1X, all RADIUS packets MUST be
   authenticated and integrity protected.  In addition, as described in
   [3579], Section 4.2.:

      To address the security vulnerabilities of RADIUS/EAP,
      implementations of this specification SHOULD support IPsec
      [<A HREF="http://RFC.net/rfc2401.html">RFC2401</A>] along with IKE [<A HREF="http://RFC.net/rfc2409.html">RFC2409</A>] for key management.  IPsec ESP
      [<A HREF="http://RFC.net/rfc2406.html">RFC2406</A>] with non-null transform SHOULD be supported, and IPsec
      ESP with a non-null encryption transform and authentication



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      support SHOULD be used to provide per-packet confidentiality,
      authentication, integrity and replay protection.  IKE SHOULD be
      used for key management.

<h2><a name='s5.2.'>5.2.  Dictionary Attacks</a></h2>

   As discussed in [<A HREF="http://RFC.net/rfc3579.html">RFC3579</A>] Section 4.3.3., the RADIUS shared secret is
   vulnerable to offline dictionary attack, based on capture of the
   Response Authenticator or Message-Authenticator attribute.  In order
   to decrease the level of vulnerability, [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>], Section 3
   recommends:

      The secret (password shared between the client and the RADIUS
      server) SHOULD be at least as large and unguessable as a well-
      chosen password.  It is preferred that the secret be at least 16
      octets.

   In addition, the risk of an offline dictionary attack can be further
   mitigated by employing IPsec ESP with a non-null transform in order
   to encrypt the RADIUS conversation, as described in [<A HREF="http://RFC.net/rfc3579.html">RFC3579</A>],
   Section 4.2.

<h2><a name='s5.3.'>5.3.  Known Plaintext Attacks</a></h2>

   Since IEEE 802.1X is based on EAP, which does not support PAP, the
   RADIUS User-Password attribute is not used to carry hidden user
   passwords.  The hiding mechanism utilizes MD5, defined in [<A HREF="http://RFC.net/rfc1321.html">RFC1321</A>],
   in order to generate a key stream based on the RADIUS shared secret
   and the Request Authenticator.  Where PAP is in use, it is possible
   to collect key streams corresponding to a given Request Authenticator
   value, by capturing RADIUS conversations corresponding to a PAP
   authentication attempt using a known password.  Since the User-
   Password is known, the key stream corresponding to a given Request
   Authenticator can be determined and stored.

   The vulnerability is described in detail in [<A HREF="http://RFC.net/rfc3579.html">RFC3579</A>], Section 4.3.4.
   Even though IEEE 802.1X Authenticators do not support PAP
   authentication, a security vulnerability can still exist where the
   same RADIUS shared secret is used for hiding User-Password as well as
   other attributes.  This can occur, for example, if the same RADIUS
   proxy handles authentication requests for both IEEE 802.1X (which may
   hide the Tunnel-Password, MS-MPPE-Send-Key and MS-MPPE-Recv-Key
   attributes) and GPRS (which may hide the User-Password attribute).

   The threat can be mitigated by protecting RADIUS with IPsec ESP with
   a non-null transform, as described in [<A HREF="http://RFC.net/rfc3579.html">RFC3579</A>], Section 4.2.  In
   addition, the same RADIUS shared secret MUST NOT be used for both
   IEEE 802.1X authentication and PAP authentication.



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<h2><a name='s5.4.'>5.4.  Replay</a></h2>

   As noted in [<A HREF="http://RFC.net/rfc3579.html">RFC3579</A>] Section 4.3.5., the RADIUS protocol provides
   only limited support for replay protection.  Replay protection for
   RADIUS authentication and accounting can be provided by enabling
   IPsec replay protection with RADIUS, as described in [<A HREF="http://RFC.net/rfc3579.html">RFC3579</A>],
   Section 4.2.

   As with the Request Authenticator, for use with IEEE 802.1X
   Authenticators, the Acct-Session-Id SHOULD be globally and temporally
   unique.

<h2><a name='s5.5.'>5.5.  Outcome Mismatches</a></h2>

   [<A HREF="http://RFC.net/rfc3579.html">RFC3579</A>] Section 2.6.3. discusses the issues that arise when the EAP
   packet encapsulated in an EAP-Message attribute does not agree with
   the RADIUS Packet Type.  For example, an EAP Success packet might be
   encapsulated within an Access-Reject; an EAP Failure might be sent
   within an Access-Accept; or an EAP Success or Failure might be sent
   within an Access-Challenge.

   As described in [<A HREF="http://RFC.net/rfc3579.html">RFC3579</A>] Section 2.6.3., these conflicting messages
   are likely to cause confusion.  To ensure that access decisions made
   by IEEE 802.1X Authenticators conform to the wishes of the RADIUS
   server, it is necessary for the Authenticator to make the decision
   solely based on the authentication result (Access-Accept/Reject) and
   not based on the contents of EAP-Message attributes, if present.

<h2><a name='s5.6.'>5.6.  802.11 Integration</a></h2>

   [IEEE8021X] was developed for use on wired IEEE 802 networks such as
   Ethernet, and therefore does not describe how to securely adapt IEEE
   <a href='#s802.1X'>802.1X</a> for use with 802.11.  This is left to an enhanced security
   specification under development within IEEE 802.11.

   For example, [IEEE8021X] does not specify whether authentication
   occurs prior to, or after association, nor how the derived keys are
   used within various ciphersuites.  It also does not specify
   ciphersuites addressing the vulnerabilities discovered in WEP,
   described in [Berkeley], [Arbaugh], [Fluhrer], and [Stubbl].
   [IEEE8021X] only defines an authentication framework, leaving the
   definition of the authentication methods to other documents, such as
   [<A HREF="http://RFC.net/rfc2716.html">RFC2716</A>].

   Since [IEEE8021X] does not address 802.11 integration issues,
   implementors are strongly advised to consult additional IEEE 802.11
   security specifications for guidance on how to adapt IEEE 802.1X for
   use with 802.11.  For example, it is likely that the IEEE 802.11



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   enhanced security specification will define its own IEEE 802.11 key
   hierarchy as well as new EAPOL-Key descriptors.

<h2><a name='s5.7.'>5.7.  Key Management Issues</a></h2>

   The EAPOL-Key descriptor described in Section 4. is likely to be
   deprecated in the future, when the IEEE 802.11 enhanced security
   group completes its work.  Known security issues include:

   [1]  Default key-only support.  IEEE 802.1X enables the derivation of
        per-Station unicast keys, known in [IEEE80211] as &quot;key mapping
        keys.&quot;  Keys used to encrypt multicast/broadcast traffic are
        known as &quot;default keys&quot;.  However, in some 802.11
        implementations, the unicast keys, derived as part of the EAP
        authentication process, are used solely in order to encrypt,
        authenticate and integrity protect the EAPOL-Key descriptor, as
        described in Section 4.  These implementations only support use
        of default keys (ordinarily only used with multicast/broadcast
        traffic) to secure all traffic, unicast or multicast/broadcast,
        resulting in inherent security weaknesses.

        Where per-Station key-mapping keys (e.g. unicast keys) are
        unsupported, any Station possessing the default key can decrypt
        traffic from other Stations or impersonate them.  When used
        along with a weak cipher (e.g. WEP), implementations supporting
        only default keys provide more material for attacks such as
        those described in [Fluhrer] and [Stubbl].  If in addition, the
        default key is not refreshed periodically, IEEE 802.1X dynamic
        key derivation provides little or no security benefit.  For an
        understanding of the issues with WEP, see [Berkeley], [Arbaugh],
        [Fluhrer], and [Stubbl].

   [2]  Reuse of keying material.  The EAPOL-Key descriptor specified in
        section 4 uses the same keying material (MS-MPPE-Recv-Key) both
        to encrypt the Key field within the EAPOL-Key descriptor, and to
        encrypt data passed between the Station and Access Point.
        Multi-purpose keying material is frowned upon, since multiple
        uses can leak information helpful to an attacker.

   [3]  Weak algorithms.  The algorithm used to encrypt the Key field
        within the EAPOL-Key descriptor is similar to the algorithm used
        in WEP, and as a result, shares some of the same weaknesses.  As
        with WEP, the RC4 stream cipher is used to encrypt the key.  As
        input to the RC4 engine, the IV and key are concatenated rather
        than being combined within a mixing function.  As with WEP, the
        IV is not a counter, and therefore there is little protection
        against reuse.




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   As a result of these vulnerabilities, implementors intending to use
   the EAPOL-Key descriptor described in this document are urged to
   consult the 802.11 enhanced security specification for a more secure
   alternative.  It is also advisable to consult the evolving literature
   on WEP vulnerabilities, in order to better understand the risks, as
   well as to obtain guidance on setting an appropriate re-keying
   interval.

<h2><a name='s6.'>6.  IANA Considerations</a></h2>

   This specification does not create any RADIUS attributes nor any new
   number spaces for IANA administration.  However, it does require
   assignment of new values to existing RADIUS attributes.  These
   include:

   Attribute              Values Required
   =========              ===============
   NAS-Port-Type          Token-Ring (20), FDDI (21)
   Tunnel-Type            VLAN (13)
   Acct-Terminate-Cause   Supplicant Restart (19)
                          Reauthentication Failure (20)
                          Port Reinitialized (21)
                          Port Administratively Disabled (22)

<h2><a name='s7.'>7.  References</a></h2>

<h2><a name='s7.1.'>7.1.  Normative References</a></h2>

   [<A HREF="http://RFC.net/rfc1321.html">RFC1321</A>]      Rivest, R., &quot;The MD5 Message-Digest Algorithm&quot;, RFC
                  1321, April 1992.

   [<A HREF="http://RFC.net/rfc2119.html">RFC2119</A>]      Bradner, S., &quot;Key words for use in RFCs to Indicate
                  Requirement Levels&quot;, <A HREF="http://RFC.net/bcp14.html">BCP 14</A>, <A HREF="http://RFC.net/rfc2119.html">RFC 2119</A>, March 1997.

   [<A HREF="http://RFC.net/rfc2284.html">RFC2284</A>]      Blunk, L. and J. Vollbrecht, &quot;PPP Extensible
                  Authentication Protocol (EAP)&quot;, <A HREF="http://RFC.net/rfc2284.html">RFC 2284</A>, March 1998.

   [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]      Rigney, C., Willens, S., Rubens, A. and W. Simpson,
                  &quot;Remote Authentication Dial In User Service (RADIUS)&quot;,
                  <A HREF="http://RFC.net/rfc2865.html">RFC 2865</A>, June 2000.

   [<A HREF="http://RFC.net/rfc2866.html">RFC2866</A>]      Rigney, C., &quot;RADIUS Accounting&quot;, <A HREF="http://RFC.net/rfc2866.html">RFC 2866</A>, June 2000.

   [<A HREF="http://RFC.net/rfc2867.html">RFC2867</A>]      Zorn, G., Aboba, B. and D. Mitton, &quot;RADIUS Accounting
                  Modifications for Tunnel Protocol Support&quot;, <A HREF="http://RFC.net/rfc2867.html">RFC 2867</A>,
                  June 2000.





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   [<A HREF="http://RFC.net/rfc2868.html">RFC2868</A>]      Zorn, G., Leifer, D., Rubens, A., Shriver, J.,
                  Holdrege, M. and I. Goyret, &quot;RADIUS Attributes for
                  Tunnel Protocol Support&quot;, <A HREF="http://RFC.net/rfc2868.html">RFC 2868</A>, June 2000.

   [<A HREF="http://RFC.net/rfc2869.html">RFC2869</A>]      Rigney, C., Willats, W. and P. Calhoun, &quot;RADIUS
                  Extensions&quot;, <A HREF="http://RFC.net/rfc2869.html">RFC 2869</A>, June 2000.

   [<A HREF="http://RFC.net/rfc3162.html">RFC3162</A>]      Aboba, B., Zorn, G. and D. Mitton, &quot;RADIUS and IPv6&quot;,
                  <A HREF="http://RFC.net/rfc3162.html">RFC 3162</A>, August 2001.

   [<A HREF="http://RFC.net/rfc3280.html">RFC3280</A>]      Housley, R., Polk, W., Ford, W. and D. Solo, &quot;Internet
                  <a href='#sX.509'>X.509</a> Public Key Infrastructure Certificate and
                  Certificate Revocation List (CRL) Profile&quot;, <A HREF="http://RFC.net/rfc3280.html">RFC 3280</A>,
                  April 2002.

   [<A HREF="http://RFC.net/rfc3576.html">RFC3576</A>]      Chiba, M., Dommety, G., Eklund, M., Mitton, D. and B.
                  Aboba, &quot;Dynamic Authorization Extensions to Remote
                  Authentication Dial In User Service (RADIUS)&quot;, RFC
                  3576, July 2003.

   [<A HREF="http://RFC.net/rfc3579.html">RFC3579</A>]      Aboba, B. and P. Calhoun, &quot;RADIUS (Remote
                  Authentication Dial In User Service) Support For
                  Extensible Authentication Protocol (EAP)&quot;, <A HREF="http://RFC.net/rfc3579.html">RFC 3579</A>,
                  September 2003.

   [IEEE8021X]    IEEE Standards for Local and Metropolitan Area
                  Networks:  Port based Network Access Control, IEEE Std
                  802.1X-2001, June 2001.

<h2><a name='s7.2.'>7.2.  Informative References</a></h2>

   [<A HREF="http://RFC.net/rfc2104.html">RFC2104</A>]      Krawczyk, H., Bellare, M. and R. Canetti, &quot;HMAC:
                  Keyed-Hashing for Message Authentication&quot;, <A HREF="http://RFC.net/rfc2104.html">RFC 2104</A>,
                  February 1997.

   [<A HREF="http://RFC.net/rfc2434.html">RFC2434</A>]      Narten, T. and H. Alvestrand, &quot;Guidelines for Writing
                  an IANA Considerations Section in RFCs&quot;, <A HREF="http://RFC.net/bcp26.html">BCP 26</A>, RFC
                  2434, October 1998.

   [<A HREF="http://RFC.net/rfc2548.html">RFC2548</A>]      Zorn, G., &quot;Microsoft Vendor-specific RADIUS
                  Attributes&quot;, <A HREF="http://RFC.net/rfc2548.html">RFC 2548</A>, March 1999.

   [<A HREF="http://RFC.net/rfc2607.html">RFC2607</A>]      Aboba, B. and J. Vollbrecht, &quot;Proxy Chaining and
                  Policy Implementation in Roaming&quot;, <A HREF="http://RFC.net/rfc2607.html">RFC 2607</A>, June
                  1999.

   [<A HREF="http://RFC.net/rfc2716.html">RFC2716</A>]      Aboba, B. and D. Simon, &quot;PPP EAP TLS Authentication
                  Protocol&quot;, <A HREF="http://RFC.net/rfc2716.html">RFC 2716</A>, October 1999.



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   [MD5Attack]    Dobbertin, H., &quot;The Status of MD5 After a Recent
                  Attack.&quot;  CryptoBytes Vol.2 No.2, Summer 1996.

   [IEEE802]      IEEE Standards for Local and Metropolitan Area
                  Networks:  Overview and Architecture, ANSI/IEEE Std
                  802, 1990.

   [IEEE8021Q]    IEEE Standards for Local and Metropolitan Area
                  Networks:  Draft Standard for Virtual Bridged Local
                  Area Networks, P802.1Q, January 1998.

   [IEEE8023]     ISO/IEC 8802-3 Information technology -
                  Telecommunications and information exchange between
                  systems - Local and metropolitan area networks -
                  Common specifications - Part 3:  Carrier Sense
                  Multiple Access with Collision Detection (CSMA/CD)
                  Access Method and Physical Layer Specifications, (also
                  ANSI/IEEE Std 802.3- 1996), 1996.

   [IEEE80211]    Information technology - Telecommunications and
                  information exchange between systems - Local and
                  metropolitan area networks - Specific Requirements
                  Part 11:  Wireless LAN Medium Access Control (MAC) and
                  Physical Layer (PHY) Specifications, IEEE Std.
                  802.11-1999, 1999.

   [Berkeley]     Borisov, N., Goldberg, I. and D. Wagner, &quot;Intercepting
                  Mobile Communications: The Insecurity of 802.11&quot;, ACM
                  SIGMOBILE, Seventh Annual International Conference on
                  Mobile Computing and Networking, July 2001, Rome,
                  Italy.

   [Arbaugh]      Arbaugh, W., Shankar, N. and J.Y.C. Wan, &quot;Your 802.11
                  Wireless Network has No Clothes&quot;, Department of
                  Computer Science, University of Maryland, College
                  Park, March 2001.

   [Fluhrer]      Fluhrer, S., Mantin, I. and A. Shamir, &quot;Weaknesses in
                  the Key Scheduling Algorithm of RC4&quot;, Eighth Annual
                  Workshop on Selected Areas in Cryptography, Toronto,
                  Canada, August 2001.

   [Stubbl]       Stubblefield, A., Ioannidis, J. and A. Rubin, &quot;Using
                  the Fluhrer, Mantin and Shamir Attack to Break WEP&quot;,
                  2002 NDSS Conference.






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<h2><a name='s8.'>8.  Table of Attributes</a></h2>

   The following table provides a guide to which attributes MAY be sent
   and received as part of IEEE 802.1X authentication.  L3 denotes
   attributes that require layer 3 capabilities, and thus may not be
   supported by all Authenticators.  For each attribute, the reference
   provides the definitive information on usage.

   <a href='#s802.1X'>802.1X</a>        #   Attribute
     X           1   User-Name [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
                 2   User-Password [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
                 3   CHAP-Password [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     X           4   NAS-IP-Address [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     X           5   NAS-Port [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     X           6   Service-Type [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
                 7   Framed-Protocol [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     L3          8   Framed-IP-Address [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     L3          9   Framed-IP-Netmask [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     L3         10   Framed-Routing [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     X          11   Filter-Id [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     X          12   Framed-MTU [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
                13   Framed-Compression [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     L3         14   Login-IP-Host [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     L3         15   Login-Service [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     L3         16   Login-TCP-Port [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
                18   Reply-Message [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
                19   Callback-Number [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
                20   Callback-Id [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     L3         22   Framed-Route [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     L3         23   Framed-IPX-Network [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     X          24   State [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     X          25   Class [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     X          26   Vendor-Specific [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     X          27   Session-Timeout [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     X          28   Idle-Timeout [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     X          29   Termination-Action [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     X          30   Called-Station-Id [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     X          31   Calling-Station-Id [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     X          32   NAS-Identifier [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     X          33   Proxy-State [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
                34   Login-LAT-Service [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
                35   Login-LAT-Node [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
                36   Login-LAT-Group [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
   <a href='#s802.1X'>802.1X</a>        #   Attribute







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   <a href='#s802.1X'>802.1X</a>        #   Attribute
     L3         37   Framed-AppleTalk-Link [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     L3         38   Framed-AppleTalk-Network [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     L3         39   Framed-AppleTalk-Zone [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     X          40   Acct-Status-Type [<A HREF="http://RFC.net/rfc2866.html">RFC2866</A>]
     X          41   Acct-Delay-Time [<A HREF="http://RFC.net/rfc2866.html">RFC2866</A>]
     X          42   Acct-Input-Octets [<A HREF="http://RFC.net/rfc2866.html">RFC2866</A>]
     X          43   Acct-Output-Octets [<A HREF="http://RFC.net/rfc2866.html">RFC2866</A>]
     X          44   Acct-Session-Id [<A HREF="http://RFC.net/rfc2866.html">RFC2866</A>]
     X          45   Acct-Authentic [<A HREF="http://RFC.net/rfc2866.html">RFC2866</A>]
     X          46   Acct-Session-Time [<A HREF="http://RFC.net/rfc2866.html">RFC2866</A>]
     X          47   Acct-Input-Packets [<A HREF="http://RFC.net/rfc2866.html">RFC2866</A>]
     X          48   Acct-Output-Packets [<A HREF="http://RFC.net/rfc2866.html">RFC2866</A>]
     X          49   Acct-Terminate-Cause [<A HREF="http://RFC.net/rfc2866.html">RFC2866</A>]
     X          50   Acct-Multi-Session-Id [<A HREF="http://RFC.net/rfc2866.html">RFC2866</A>]
     X          51   Acct-Link-Count [<A HREF="http://RFC.net/rfc2866.html">RFC2866</A>]
     X          52   Acct-Input-Gigawords [<A HREF="http://RFC.net/rfc2869.html">RFC2869</A>]
     X          53   Acct-Output-Gigawords [<A HREF="http://RFC.net/rfc2869.html">RFC2869</A>]
     X          55   Event-Timestamp [<A HREF="http://RFC.net/rfc2869.html">RFC2869</A>]
                60   CHAP-Challenge [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     X          61   NAS-Port-Type [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
                62   Port-Limit [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
                63   Login-LAT-Port [<A HREF="http://RFC.net/rfc2865.html">RFC2865</A>]
     X          64   Tunnel-Type [<A HREF="http://RFC.net/rfc2868.html">RFC2868</A>]
     X          65   Tunnel-Medium-Type [<A HREF="http://RFC.net/rfc2868.html">RFC2868</A>]
     L3         66   Tunnel-Client-Endpoint [<A HREF="http://RFC.net/rfc2868.html">RFC2868</A>]
     L3         67   Tunnel-Server-Endpoint [<A HREF="http://RFC.net/rfc2868.html">RFC2868</A>]
     L3         68   Acct-Tunnel-Connection [<A HREF="http://RFC.net/rfc2867.html">RFC2867</A>]
     L3         69   Tunnel-Password [<A HREF="http://RFC.net/rfc2868.html">RFC2868</A>]
                70   ARAP-Password [<A HREF="http://RFC.net/rfc2869.html">RFC2869</A>]
                71   ARAP-Features [<A HREF="http://RFC.net/rfc2869.html">RFC2869</A>]
                72   ARAP-Zone-Access [<A HREF="http://RFC.net/rfc2869.html">RFC2869</A>]
                73   ARAP-Security [<A HREF="http://RFC.net/rfc2869.html">RFC2869</A>]
                74   ARAP-Security-Data [<A HREF="http://RFC.net/rfc2869.html">RFC2869</A>]
                75   Password-Retry [<A HREF="http://RFC.net/rfc2869.html">RFC2869</A>]
                76   Prompt [<A HREF="http://RFC.net/rfc2869.html">RFC2869</A>]
     X          77   Connect-Info [<A HREF="http://RFC.net/rfc2869.html">RFC2869</A>]
     X          78   Configuration-Token [<A HREF="http://RFC.net/rfc2869.html">RFC2869</A>]
     X          79   EAP-Message [<A HREF="http://RFC.net/rfc3579.html">RFC3579</A>]
     X          80   Message-Authenticator [<A HREF="http://RFC.net/rfc3579.html">RFC3579</A>]
     X          81   Tunnel-Private-Group-ID [<A HREF="http://RFC.net/rfc2868.html">RFC2868</A>]
     L3         82   Tunnel-Assignment-ID [<A HREF="http://RFC.net/rfc2868.html">RFC2868</A>]
     X          83   Tunnel-Preference [<A HREF="http://RFC.net/rfc2868.html">RFC2868</A>]
                84   ARAP-Challenge-Response [<A HREF="http://RFC.net/rfc2869.html">RFC2869</A>]
   <a href='#s802.1X'>802.1X</a>        #   Attribute






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   <a href='#s802.1X'>802.1X</a>        #   Attribute
     X          85   Acct-Interim-Interval [<A HREF="http://RFC.net/rfc2869.html">RFC2869</A>]
     X          86   Acct-Tunnel-Packets-Lost [<A HREF="http://RFC.net/rfc2867.html">RFC2867</A>]
     X          87   NAS-Port-Id [<A HREF="http://RFC.net/rfc2869.html">RFC2869</A>]
     L3         88   Framed-Pool [<A HREF="http://RFC.net/rfc2869.html">RFC2869</A>]
     L3         90   Tunnel-Client-Auth-ID [<A HREF="http://RFC.net/rfc2868.html">RFC2868</A>]
     L3         91   Tunnel-Server-Auth-ID [<A HREF="http://RFC.net/rfc2868.html">RFC2868</A>]
     X          95   NAS-IPv6-Address [<A HREF="http://RFC.net/rfc3162.html">RFC3162</A>]
                96   Framed-Interface-Id [<A HREF="http://RFC.net/rfc3162.html">RFC3162</A>]
     L3         97   Framed-IPv6-Prefix [<A HREF="http://RFC.net/rfc3162.html">RFC3162</A>]
     L3         98   Login-IPv6-Host [<A HREF="http://RFC.net/rfc3162.html">RFC3162</A>]
     L3         99   Framed-IPv6-Route [<A HREF="http://RFC.net/rfc3162.html">RFC3162</A>]
     L3        100   Framed-IPv6-Pool [<A HREF="http://RFC.net/rfc3162.html">RFC3162</A>]
     X         101   Error-Cause [<A HREF="http://RFC.net/rfc3576.html">RFC3576</A>]
   <a href='#s802.1X'>802.1X</a>        #   Attribute

   Key
   ===
   X         = May be used with IEEE 802.1X authentication
   L3        = Implemented only by Authenticators with Layer 3
               capabilities






























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<h2><a name='s9.'>9.  Intellectual Property Statement</a></h2>

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights.  Information on the
   IETF's procedures with respect to rights in standards-track and
   standards- related documentation can be found in <A HREF="http://RFC.net/bcp11.html">BCP-11</A>.  Copies of
   claims of rights made available for publication and any assurances of
   licenses to be made available, or the result of an attempt made to
   obtain a general license or permission for the use of such
   proprietary rights by implementors or users of this specification can
   be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard.  Please address the information to the IETF Executive
   Director.

<h2><a name='s10.'>10.  Acknowledgments</a></h2>

   The authors would like to acknowledge Bob O'Hara of Airespace, David
   Halasz of Cisco, Tim Moore, Sachin Seth and Ashwin Palekar of
   Microsoft, Andrea Li, Albert Young and Dave Bagby of 3Com for
   contributions to this document.























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<h2><a name='s11.'>11.  Authors' Addresses</a></h2>

   Paul Congdon
   Hewlett Packard Company
   HP ProCurve Networking
   8000 Foothills Blvd, M/S 5662
   Roseville, CA  95747

   Phone: +1 916 785 5753
   Fax:   +1 916 785 8478
   EMail: paul_congdon@hp.com

   Bernard Aboba
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA 98052

   Phone: +1 425 706 6605
   Fax:   +1 425 936 7329
   EMail: bernarda@microsoft.com

   Andrew Smith
   Trapeze Networks
   5753 W. Las Positas Blvd.
   Pleasanton, CA 94588-4084

   Fax: +1 415 345 1827
   EMail: ah_smith@acm.org

   John Roese
   Enterasys

   Phone: +1 603 337 1506
   EMail: jjr@enterasys.com

   Glen Zorn
   Cisco Systems, Inc.
   500 108th Avenue N.E., Suite 500
   Bellevue, WA 98004

   Phone: +1 425 438 8218
   Fax:   +1 425 438 1848
   EMail: gwz@cisco.com








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<h2><a name='s12.'>12.  Full Copyright Statement</a></h2>

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assignees.

   This document and the information contained herein is provided on an
   &quot;AS IS&quot; basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.



















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